Leadless cardiac pacemaker with delivery and/or retrieval features

ABSTRACT

An implantable leadless cardiac pacing device and associated delivery and retrieval devices. The implantable device includes a docking member extending from the proximal end of the housing of the implantable device configured to engage with the delivery and/or retrieval device to facilitate delivery and/or retrieval of the implantable leadless cardiac pacing device.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 14/451,601, filed on Aug. 5, 2014, which claims the benefit ofpriority under 35 U.S.C. § 119(e) of U.S. Provisional Patent ApplicationSer. No. 61/866,644, filed on Aug. 16, 2013, which are hereinincorporated by reference in their entirety.

TECHNICAL FIELD

The disclosure is directed to implantable cardiac devices. Moreparticularly, the disclosure is directed to leadless cardiac stimulatorsor pacemakers including delivery and/or retrieval features.

BACKGROUND

Cardiac pacemakers provide electrical stimulation to heart tissue tocause the heart to contract and thus pump blood through the vascularsystem. Conventional pacemakers typically include an electrical leadthat extends from a pulse generator implanted subcutaneously orsub-muscularly to an electrode positioned adjacent the inside or outsidewall of the cardiac chamber. As an alternative to conventionalpacemakers, self-contained or leadless cardiac pacemakers have beenproposed. Leadless cardiac pacemakers are small capsules typically fixedto an intracardiac implant site in a cardiac chamber with a fixationmechanism engaging the intracardiac tissue. The small capsule typicallyincludes bipolar pacing/sensing electrodes, a power source (e.g. abattery), and associated electrical circuitry for controlling thepacing/sensing electrodes, and thus provide electrical stimulation toheart tissue and/or sense a physiological condition.

Accordingly, there it is desirable to provide alternative structures tofacilitate delivering leadless cardiac pacemakers to an implantationsite in a heart chamber and/or retrieving leadless cardiac pacemakersfrom an implantation site in a heart chamber.

SUMMARY

The disclosure is directed to several alternative designs, materials andmethods of manufacturing medical device structures and assemblies, anduses thereof.

Accordingly, one illustrative embodiment is an implantable leadlesscardiac pacing device. The implantable device includes a housing, anelectrode positioned proximate the distal end of the housing configuredto be positioned adjacent cardiac tissue, and a docking member extendingfrom the proximal end of the housing along a longitudinal axis of thehousing. The docking member is configured to facilitate retrieval of theimplantable leadless cardiac pacing device. The docking member includesa head portion and a neck portion extending between the housing and thehead portion. The head portion has a radial dimension from thelongitudinal axis and the neck portion has a radial dimension from thelongitudinal axis less than the radial dimension of the head portion.The head portion includes a recess extending into the head portion froma proximal surface of the head portion for receiving a rotationaldriving instrument.

Another illustrative embodiment is an implantable leadless cardiacpacing device. The implantable device includes a housing, an electrodepositioned proximate the distal end of the housing configured to bepositioned adjacent cardiac tissue, and a docking member extending fromthe proximal end of the housing along a longitudinal axis of thehousing. The docking member is configured to facilitate retrieval of theimplantable leadless cardiac pacing device. The docking member includesa head portion and a neck portion extending between the housing and thehead portion. The head portion has a radial dimension from thelongitudinal axis and the neck portion has a radial dimension from thelongitudinal axis less than the radial dimension of the head portion.The head portion includes a plurality of radially extending spokesextending radially outward from the longitudinal axis of the housing.

Another illustrative embodiment is a system for implanting animplantable leadless cardiac pacing device. The system includes animplantable cardiac pacing device and a delivery device. The implantablecardiac pacing device has a housing, an electrode positioned proximate adistal end of the housing, and a docking member extending from aproximal end of the housing opposite the distal end. The docking memberincludes a head portion and a neck portion extending between the housingand the head portion. The delivery device includes an elongate shaft anda driver mechanism at a distal end of the elongate shaft. The drivermechanism is configured for engagement with the head portion of thedocking member. The driver mechanism includes a first lug configured toengage a recess extending into the head portion from a proximal surfaceof the head portion. In some instances, the driver mechanism includesfirst and second spaced apart lugs configured to engage first and secondportions of the recess, respectively, with a member extending across therecess positioned between the first and second lugs.

Another illustrative embodiment is a system for retrieving animplantable leadless cardiac pacing device. The system includes animplantable cardiac pacing device and a retrieval device. Theimplantable cardiac pacing device has a housing having a longitudinalaxis, an electrode positioned proximate a distal end of the housing, anda docking member extending from a proximal end of the housing oppositethe distal end. The docking member includes a head portion and a neckportion extending between the housing and the head portion. The headportion includes a plurality of radially extending spokes extendingradially outward from the longitudinal axis of the housing. Theretrieval device includes a snare having an elongate shaft and one ormore loops at a distal end of the elongate shaft. The one or more loopsof the retrieval device are capable of encircling one or more of theradially extending spokes to capture the docking member with the snare.

Another illustrative embodiment is a method of implanting an implantablecardiac pacing device. The method includes advancing an implantablecardiac pacing device into a chamber of a heart with a delivery device.The implantable cardiac pacing device includes a helical fixationmechanism extending from a distal end of a housing of the implantablecardiac pacing device and a docking member extending from a proximal endof the housing. The docking member includes a head portion and a neckportion extending between the housing and the head portion. The methodfurther includes rotating an elongate shaft of the delivery device torotate the helical fixation mechanism into cardiac tissue. The deliverydevice includes a driver mechanism at a distal end of the elongateshaft. The driver mechanism includes a first lug engaged in a recess ofthe head portion of the docking member to transfer rotational motionfrom the driver mechanism to the implantable cardiac pacing device.

Yet another illustrative embodiment is a method of retrieving animplantable cardiac pacing device from a heart. The implantable cardiacpacing device has a housing having a longitudinal axis, an electrodepositioned proximate a distal end of the housing, and a docking memberextending from a proximal end of the housing opposite the distal end.The docking member includes a head portion and a neck portion extendingbetween the housing and the head portion. The head portion includes aplurality of radially extending spokes extending radially outward fromthe longitudinal axis of the housing. The method includes advancing asnare into a heart having the implantable cardiac pacing deviceimplanted therein and encircling the docking member with a loop of thesnare. The loop is then cinched around a portion of the docking memberand the snare is actuated proximally to pull the implantable cardiacpacing device into a lumen of a retrieval catheter.

The above summary of some example embodiments is not intended todescribe each disclosed embodiment or every implementation of theaspects of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The aspects of the disclosure may be more completely understood inconsideration of the following detailed description of variousembodiments in connection with the accompanying drawings, in which:

FIG. 1 illustrates an exemplary implantable device implanted in achamber of a heart;

FIG. 2 illustrates an exemplary retrieval device capturing animplantable device during a retrieval procedure;

FIG. 3 illustrates another exemplary retrieval device capturing animplantable device during a retrieval procedure;

FIGS. 4A-4C illustrate an exemplary docking member of an implantabledevice;

FIGS. 5A-5C illustrate another exemplary docking member of animplantable device;

FIGS. 6A-6C illustrate another exemplary docking member of animplantable device;

FIGS. 7A-7C illustrate another exemplary docking member of animplantable device;

FIGS. 8A-8C illustrate another exemplary docking member of animplantable device;

FIGS. 9A-9C illustrate another exemplary docking member of animplantable device;

FIGS. 10A-10C illustrate another exemplary docking member of animplantable device;

FIGS. 11A-11C illustrate another exemplary docking member of animplantable device;

FIGS. 12A-12C illustrate another exemplary docking member of animplantable device;

FIGS. 13A-13C illustrate another exemplary docking member of animplantable device;

FIGS. 14A-14C illustrate another exemplary docking member of animplantable device;

FIGS. 15A-15C illustrate another exemplary docking member of animplantable device;

FIGS. 16A-16C illustrate another exemplary docking member of animplantable device;

FIG. 17A illustrates an exemplary delivery device for delivering animplantable device;

FIG. 17B illustrates the delivery device of FIG. 17A in engagement withthe docking member of the implantable device of FIGS. 15A-15C;

FIG. 17C illustrates the delivery device of FIG. 17A in engagement withthe docking member of the implantable device of FIGS. 16A-16C; and

FIGS. 18A-18D illustrate alternative embodiments of a driver mechanismfor a rotational driving instrument.

While the aspects of the disclosure are amenable to variousmodifications and alternative forms, specifics thereof have been shownby way of example in the drawings and will be described in detail. Itshould be understood, however, that the intention is not to limitaspects of the disclosure to the particular embodiments described. Onthe contrary, the intention is to cover all modifications, equivalents,and alternatives falling within the spirit and scope of the disclosure.

DETAILED DESCRIPTION

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere inthis specification.

All numeric values are herein assumed to be modified by the term“about”, whether or not explicitly indicated. The term “about” generallyrefers to a range of numbers that one of skill in the art would considerequivalent to the recited value (i.e., having the same function orresult). In many instances, the term “about” may be indicative asincluding numbers that are rounded to the nearest significant figure.

The recitation of numerical ranges by endpoints includes all numberswithin that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4,and 5).

Although some suitable dimensions, ranges and/or values pertaining tovarious components, features and/or specifications are disclosed, one ofskill in the art, incited by the present disclosure, would understanddesired dimensions, ranges and/or values may deviate from thoseexpressly disclosed.

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

The following detailed description should be read with reference to thedrawings in which similar elements in different drawings are numberedthe same. The detailed description and the drawings, which are notnecessarily to scale, depict illustrative embodiments and are notintended to limit the scope of the disclosure. The illustrativeembodiments depicted are intended only as exemplary. Selected featuresof any illustrative embodiment may be incorporated into an additionalembodiment unless clearly stated to the contrary.

Referring to FIG. 1, an exemplary implantable leadless cardiac pacingdevice 10 (e.g., a leadless pacemaker) is illustrated implanted in achamber of a heart H, such as the apex of the right ventricle RV. Theimplantable device 10 may include a shell or housing 12 having aproximal end 14 and a distal end 16. The implantable device 10 mayinclude a first electrode 20 positioned proximate the distal end 16 ofthe housing 12 and a second electrode 22 positioned proximate theproximal end 14 of the housing 12. The electrodes 20, 22 may be sensingand/or pacing electrodes to provide electro-therapy and/or sensingcapabilities. The first electrode 20 may be configured to be positionedagainst or otherwise contact the cardiac tissue of the heart H while thesecond electrode 22 may be spaced away from the first electrode 20, andthus spaced away from the cardiac tissue.

The implantable device 10 may include a pulse generator (e.g.,electrical circuitry) and a power source (e.g., a battery) within thehousing 12 to provide electrical signals to the electrodes 20, 22 andthus control the pacing/sensing electrodes 20, 22. Electricalcommunication between pulse generator and the electrodes 20, 22 mayprovide electrical stimulation to heart tissue and/or sense aphysiological condition.

The implantable device 10 may include a fixation mechanism 24 proximatethe distal end 16 of the housing 12 configured to attach the implantabledevice 10 to a tissue wall of the heart H, or otherwise anchor theimplantable device 10 to the anatomy of the patient. As shown in FIG. 1,in some instances, the fixation mechanism 24 may include one or more, ora plurality of hooks 26 anchored into the cardiac tissue of the heart Hto attach the implantable device 10 to a tissue wall. In otherinstances, the fixation mechanism 24 may include one or more, or aplurality of passive tines, configured to entangle with trabeculaewithin the chamber of the heart H and/or a helical fixation anchorconfigured to be screwed into a tissue wall to anchor the implantabledevice 10 to the heart H.

The implantable device 10 may include a docking member 30 proximate theproximal end 14 of the housing 12 configured to facilitate deliveryand/or retrieval of the implantable device 10. For example, the dockingmember 30 may extend from the proximal end 14 of the housing 12 along alongitudinal axis of the housing 12. The docking member 30 may include ahead portion 32 and a neck portion 34 extending between the housing 12and the head portion 32. The head portion 32 may be an enlarged portionrelative to the neck portion 34. For example, the head portion 32 mayhave a radial dimension from the longitudinal axis of the implantabledevice 10 which is greater than a radial dimension of the neck portionfrom the longitudinal axis of the implantable device 10. The dockingmember 30 may be configured to facilitate delivery of the implantabledevice 10 to the intracardiac site and/or retrieval of the implantabledevice 10 from the intracardiac site. Some exemplary embodiments of thedocking member 30 are described in further detail herein.

If it is desired to retrieve the implantable device 10 from the heart H,a retrieval device 50 may be advanced into the chamber of the heart H tocapture the implantable device 10 and remove the implantable device 10from the heart H. One exemplary retrieval device 50 is illustrated inFIG. 2. The retrieval device 50 may include a snare 52 advanceable froma lumen 58 of a retrieval catheter 54. The snare 52 may include one ormore, or a plurality of loops 56 extending from a distal end of thesnare 52 configured to engage the docking member 30 of the implantabledevice 10. The snare 52 shown in FIG. 2 includes three loops 56 formedby elongate filaments extending from the shaft of the snare 52. Once theloop(s) 56 of the snare 52 has captured the docking member 30, the snare52 may be actuated proximally relative to the retrieval catheter 54 topull the implantable device 10 into the lumen 58 of the retrievalcatheter 54. The enlarged size of the head portion 32 relative to theneck portion 34 may permit the loop 56 of the snare 52 to encircle theneck portion 34 below (i.e., distal of) the head portion 32 and retainthe loop 56 around the docking member 30 as the snare 52 is pulledproximally. As the implantable device 10 is pulled into the retrievalcatheter 54, the fixation mechanism 24 may disengage from the hearttissue to detach the implantable device 10 from the heart wall. Forexample, the hooks 26 may elongate as the implantable device 10 is drawnproximally into the lumen 58 of the retrieval catheter 54. Thereafter,the retrieval device 50, with the implantable device 10 captured in thelumen of the retrieval catheter 54 with the snare 52, may be withdrawnfrom the heart H.

Another exemplary retrieval device 50 is illustrated in FIG. 3. Similarto FIG. 2, the retrieval device 50 may include a snare 52 advanceablefrom a lumen 58 of a retrieval catheter 54. The snare 52 may include oneor more, or a plurality of loops 56 extending from a distal end of thesnare 52 configured to engage the docking member 30 of the implantabledevice 10. The snare 52 shown in FIG. 3 includes a single loop 56 formedby an elongate filament extending from the shaft of the snare 52. Oncethe loop 56 of the snare 52 has captured the docking member 30, thesnare 52 may be actuated proximally relative to the retrieval catheter54 to pull the implantable device 10 into the lumen 58 of the retrievalcatheter 54. The enlarged size of the head portion 32 relative to theneck portion 34 may permit the loop 56 of the snare 52 to encircle theneck portion 34 below (i.e., distal of) the head portion 32 and retainthe loop 56 around the docking member 30 as the snare 52 is pulledproximally. As the implantable device 10 is pulled into the retrievalcatheter 54, the fixation mechanism 30 may disengage from the hearttissue to detach the implantable device 10 from the heart wall. Forexample, the hooks 26 may elongate as the implantable device 10 is drawnproximally into the lumen 58 of the retrieval catheter 54. Thereafter,the retrieval device 50, with the implantable device 10 captured in thelumen of the retrieval catheter 54 with the snare 52, may be withdrawnfrom the heart H.

FIGS. 4A-4C illustrate one exemplary docking member 30 located at theproximal end 14 of the implantable device 10. The docking member 30shown in FIGS. 4A-4C may include a head portion 32 and a neck portion 34extending between the housing 12 and the head portion 32. The headportion 32 may be a generally spherically shaped ball, having a diameterD1 greater than the diameter D2 of the neck portion 34. The dockingmember 30 may also include a passage 36 extending through a portion ofthe docking member 30 to receive a tether 80 (shown in phantom lines)which will be further described later herein. For example, the passage36 may extend through the head portion 32 from a first side to a secondside of the head portion 32. The spherical shape of the head portion 32may provide an atraumatic profile, inhibiting tissue growth orentanglement around the docking member 30.

FIGS. 5A-5C illustrate another exemplary docking member 30 located atthe proximal end 14 of the implantable device 10. The docking member 30shown in FIGS. 5A-5C may include a head portion 32 and a neck portion 34extending between the housing 12 and the head portion 32. The headportion 32 may be a generally disc shaped element having an uppersurface 62 and an opposing lower surface 64. In some instances, theupper surface 62 and/or the lower surface 64 may be a spherically convexsurface while in other instances the upper surface 62 and/or the lowersurface 64 may be a spherically concave surface or a planar surface, forexample. The head portion 32 may have a diameter D1 greater than thediameter D2 of the neck portion 34. Although not shown, the dockingmember 30 may also include a passage extending through a portion of thedocking member 30 to receive a tether (described later herein). Forexample, a passage may extend through the head portion 32 from a firstside to a second side of the head portion 32, or a passage may extendthrough the neck portion 34 from a first side to a second side of theneck portion 34. The shape of the head portion 32 may provide anatraumatic profile, inhibiting tissue growth or entanglement around thedocking member 30.

FIGS. 6A-6C illustrate another exemplary docking member 30 located atthe proximal end 14 of the implantable device 10. The docking member 30shown in FIGS. 6A-6C may include a head portion 32 and a neck portion 34extending between the housing 12 and the head portion 32. The headportion 32 may be generally knob shaped, having a diameter D1 greaterthan the diameter D2 of the neck portion 34. The docking member 30 mayalso include a passage 36 extending through a portion of the dockingmember 30 to receive a tether 80 (shown in phantom) further describedlater herein. For example, the head portion 32 may include a centralopening 66 extending into the head portion 32. A pin 68 may extend intoor across the opening 66. For example, as shown in FIG. 6C the pin 68may extend from a first side to a second side of the opening 66. Inother instances, the pin 68 may extend into the opening 66 from a firstside toward a second side of the opening 66, but not entirely across theopening 66 to the second side. The passage 36 may extend under the pin68 such that the tether may be passed around the pin 68. The shape ofthe head portion 32 may provide an atraumatic profile, inhibiting tissuegrowth or entanglement around the docking member 30.

FIGS. 7A-7C illustrate another exemplary docking member 30 located atthe proximal end 14 of the implantable device 10. The docking member 30shown in FIGS. 7A-7C may include a head portion 32 and a neck portion 34extending between the housing 12 and the head portion 32. The headportion 32 may include a plurality of enlarged portions 70 spaced apartby a reduced diameter necked portion 72. In some instances, the enlargedportions 70 may be generally knob shaped, having a diameter D1 greaterthan the diameter D3 of the necked portion between the enlarged portions70 and the diameter D2 of the neck portion 34. Multiple enlargedportions 70 may facilitate engaging the docking member 30 with theloop(s) 56 of the snare 52 during retrieval of the implantable device10. The shape of the head portion 32 may provide an atraumatic profile,inhibiting tissue growth or entanglement around the docking member 30.

The docking member 30 may also include a passage 36 extending through aportion of the docking member 30 to receive a tether (described laterherein). For example, the head portion 32 may include a central opening66 extending into the head portion 32. A pin 68 may extend into oracross the opening 66. For example, as shown in FIG. 7C the pin 68 mayextend from a first side to a second side of the opening 66. In otherinstances, the pin 68 may extend into the opening 66 from a first sidetoward a second side of the opening 66, but not entirely across theopening 66 to the second side. The passage 36 may extend under the pin68 such that the tether may be passed around the pin 68.

FIGS. 8A-8C illustrate another exemplary docking member 30 located atthe proximal end 14 of the implantable device 10. The docking member 30shown in FIGS. 8A-8C may include a head portion 32 and a neck portion 34extending between the housing 12 and the head portion 32. The headportion 32 may have a diameter D1 greater than the diameter D2 of theneck portion 34. The head portion 32 may include a plurality of spokes70 extending radially from the longitudinal axis of the implantabledevice 10, with spaces defined between adjacent spokes 70. The spokes 70may be symmetrically or asymmetrically arranged around the longitudinalaxis X. For example, the head portion 32 may include four spokes 70uniformly arranged around the longitudinal axis X about 90 degreesapart. As shown in FIG. 8X, the free ends 72 of the radially extendingspokes 70 may angle (e.g., curve) toward the distal end 16 of theimplantable device 10, in some instances. For example, an upper surface74 and/or a lower surface 76 of the spokes 70 may extend at an obliqueangle to the longitudinal axis X of the implantable device 10 toward thedistal end 16, such that the free ends 72 of the spokes 70 arepositioned closer to the distal end 16 of the implantable device 10 thanthe base portion of the spokes 70 proximate the central longitudinalaxis X. The configuration and/or arrangement of the spokes 70 mayfacilitate retention of the loop 56 of the snare 52 in engagement of thedocking member 30 during retrieval of the implantable device 10. Forexample, the loop 56 may encircle one or more of the spokes 70 inaddition to or instead of the neck portion 34.

Although not shown, the docking member 30 may also include a passageextending through a portion of the docking member 30 to receive a tether(described later herein). For example, a passage may extend through theone or more of the spokes 70 from a first side to a second side of thespoke 70, or a passage may extend through the neck portion 34 from afirst side to a second side of the neck portion 34.

FIGS. 9A-9C illustrate another exemplary docking member 30 located atthe proximal end 14 of the implantable device 10, similar to the dockingmember 30 illustrated in FIGS. 8A-8C. The docking member 30 shown inFIGS. 9A-9C may similarly include a plurality of spokes 70 extendingradially from the longitudinal axis of the implantable device 10, withspaces defined between adjacent spokes 70, except the spokes 70 shown inFIGS. 9A-9C may have a width W less than the width of the spokes shownin FIGS. 8A-8C.

Although not shown, the docking member 30 may also include a passageextending through a portion of the docking member 30 to receive a tether(described later herein). For example, a passage may extend through theone or more of the spokes 70 from a first side to a second side of thespoke 70, or a passage may extend through the neck portion 34 from afirst side to a second side of the neck portion 34.

FIGS. 10A-10C illustrate another exemplary docking member 30 located atthe proximal end 14 of the implantable device 10, similar to the dockingmember 30 illustrated in FIGS. 8A-8C. The docking member 30 shown inFIGS. 10A-10C may similarly include a plurality of spokes 70 extendingradially from the longitudinal axis of the implantable device 10, withspaces defined between adjacent spokes 70. The width W of the spokes 70shown in FIGS. 10A-10C may increase from the base portion toward thefree ends 72 of the spokes. Thus, in instances in which the loop 56 ofthe snare 52 encircles one or more of the spokes 70, the enlarged freeend 72 of the spokes 70 may prevent the loop 56 of the snare 52 fromslipping off the spoke(s) 70 during retrieval of the implantable device10.

Although not shown, the docking member 30 may also include a passageextending through a portion of the docking member 30 to receive a tether(described later herein). For example, a passage may extend through theone or more of the spokes 70 from a first side to a second side of thespoke 70, or a passage may extend through the neck portion 34 from afirst side to a second side of the neck portion 34.

FIGS. 11A-11C illustrate another exemplary docking member 30 located atthe proximal end 14 of the implantable device 10, similar to the dockingmember 30 illustrated in FIGS. 8A-8C. The docking member 30 shown inFIGS. 11A-11C may include a pair of spokes 70 extending radially fromthe longitudinal axis of the implantable device 10 in oppositedirections. Similar to the spokes 70 shown in FIGS. 10A-10C, the width Wof the spokes 70 shown in FIGS. 11A-11C may increase from the baseportion toward the free ends 72 of the spokes. Thus, in instances inwhich the loop 56 of the snare 52 encircles one or more of the spokes70, the enlarged free end 72 of the spokes 70 may prevent the loop 56 ofthe snare 52 from slipping off the spoke(s) 70 during retrieval of theimplantable device 10.

Although not shown, the docking member 30 may also include a passageextending through a portion of the docking member 30 to receive a tether(described later herein). For example, a passage may extend through theone or more of the spokes 70 from a first side to a second side of thespoke 70, or a passage may extend through the neck portion 34 from afirst side to a second side of the neck portion 34.

FIGS. 12A-12C illustrate another exemplary docking member 30 located atthe proximal end 14 of the implantable device 10, similar to the dockingmember 30 illustrated in FIGS. 11A-11C. The docking member 30 shown inFIGS. 12A-12C may include a pair of spokes 70 extending radially fromthe longitudinal axis of the implantable device 10 in oppositedirections. The free ends 72 of the spokes 70 may include a crossingmember 74 extending transverse to the radial direction of the spokes 70.In some instances, the crossing member 74 may extend in oppositedirections from the body of the spoke 70, or the crossing member 74 mayextend in one transverse direction from the body of the spoke 70. Forexample, in some instances, the spokes 70 may have a T shape, a mushroomshape, an L shape, a V shape, or other desired shape. In some instances,the crossing member 74 may form an undercut 76 with the body of thespoke 70. The loop 56 of the snare 52 may be engaged in the undercuts 76as the loop 56 is tightened around the spoke 70. In instances in whichthe loop 56 of the snare 52 encircles one or more of the spokes 70, thecrossing member 74 at the free end 72 of the spokes 70 may prevent theloop 56 of the snare 52 from slipping off the spoke(s) 70 duringretrieval of the implantable device 10.

Although not shown, the docking member 30 may also include a passageextending through a portion of the docking member 30 to receive a tether(described later herein). For example, a passage may extend through theone or more of the spokes 70 from a first side to a second side of thespoke 70, or a passage may extend through the neck portion 34 from afirst side to a second side of the neck portion 34.

FIGS. 13A-13C illustrate another exemplary docking member 30 located atthe proximal end 14 of the implantable device 10, similar to the dockingmember 30 illustrated in FIGS. 12A-12C. The docking member 30 shown inFIGS. 13A-13C may include a plurality of spokes 70 extending radiallyfrom the longitudinal axis of the implantable device 10, with spacesdefined between adjacent spokes 70. The spokes 70 may be symmetricallyor asymmetrically arranged around the longitudinal axis. For example,the head portion 32 may include three spokes 70 uniformly arrangedaround the longitudinal axis about 120 degrees apart. Similar to thespokes illustrated in FIGS. 12A-12C, the free ends 72 of the spokes 70may include a crossing member 74 extending transverse to the radialdirection of the spokes 70. In some instances, the crossing member 74may extend in opposite directions from the body of the spoke 70, or thecrossing member 74 may extend in one transverse direction from the bodyof the spoke 70. For example, in some instances, the spokes 70 may havea T shape, a mushroom shape, an L shape, a V shape, or other desiredshape. In some instances, the crossing member 74 may form an undercut 76with the body of the spoke 70. The loop 56 of the snare 52 may beengaged in the undercuts 76 as the loop 56 is tightened around the spoke70. In instances in which the loop 56 of the snare 52 encircles one ormore of the spokes 70, the crossing member 74 at the free end 72 of thespokes 70 may prevent the loop 56 of the snare 52 from slipping off thespoke(s) 70 during retrieval of the implantable device 10.

Although not shown, the docking member 30 may also include a passageextending through a portion of the docking member 30 to receive a tether(described later herein). For example, a passage may extend through theone or more of the spokes 70 from a first side to a second side of thespoke 70, or a passage may extend through the neck portion 34 from afirst side to a second side of the neck portion 34.

FIGS. 14A-14C illustrate another exemplary docking member 30 located atthe proximal end 14 of the implantable device 10, similar to the dockingmember 30 illustrated in FIGS. 8A-8C. The docking member 30 shown inFIGS. 14A-14C may similarly include a plurality of spokes 70 extendingradially from the longitudinal axis of the implantable device 10, withspaces defined between adjacent spokes 70. The docking member 30 mayinclude any number of radially extending spokes 70 symmetrically orasymmetrically arranged around the longitudinal axis of the implantabledevice 10. For example, the docking member 30 may include 3, 4, 5, 6, 7,8, 9, 10, 11, 12 or more radially extending spokes 70 in some instances.

As shown in FIG. 14C, the free ends 72 of the spokes 70 may include adistally projecting lip 78 relative to the body portion of the spokes70. The distally projecting lips 78 may prevent the loop 56 of the snare52 from slipping off the spoke(s) 70 during retrieval of the implantabledevice 10.

The configuration and/or arrangement of the spokes 70 may facilitateretention of the loop 56 of the snare 52 in engagement of the dockingmember 30 during retrieval of the implantable device 10. For example,the loop 56 may encircle one or more of the spokes 70 in addition to orinstead of the neck portion 34.

In some instances it may be desirable to apply rotational motion to theimplantable device 10 during delivery and/or retrieval of theimplantable device 10. For example, in some embodiments such as theembodiment shown in FIG. 15A, the implantable device 10 may include ahelical fixation anchor 90 at the distal end 16 of the housing 12configured to be screwed into a tissue wall through rotational motion ofthe implantable device 10 to anchor the implantable device 10 to theheart H. In such instances, the docking member 30 may include anengagement feature configured to mate with an engagement feature of adelivery device to transfer rotational motion from a rotatable shaft ofthe delivery device to the implantable device 10.

For example, in the embodiment of FIGS. 15A-15C, the implantable device10 may include a docking member 30 extending from the proximal end 14 ofthe housing 12 along a longitudinal axis of the housing 12. The dockingmember 30 may include a head portion 32 and a neck portion 34 extendingbetween the housing 12 and the head portion 32. The head portion 32 maybe an enlarged portion relative to the neck portion 34. For example, thehead portion 32 may have a radial dimension from the longitudinal axisof the implantable device 10 which is greater than a radial dimension ofthe neck portion from the longitudinal axis of the implantable device10.

The head portion 32 may include a recess 82 extending into the headportion 32 from a proximal surface 84 of the head portion 32. The recess82 may be configured to receive a rotational driving instrument therein.For example, the recess 82 may be configured to receive a distal drivermechanism of a rotational driving instrument therein. In some instances,the recess 82 may extend generally perpendicular to the longitudinalaxis of the housing 12. In some embodiments, the recess 82 may extendacross the head portion 32 from a first side of the head portion 32 to asecond side of the head portion 32. As shown in FIG. 15C, the headportion 32 may include a distal surface 85 opposite the proximal surface84 from which the neck portion 34 extends from. In some instances, therecess 82 may extend into the head portion 32 from the proximal surface84 toward the distal surface 85, but does not extend to the distalsurface 85. However, in other embodiments the recess 82 may extend tothe distal surface 85.

The head portion 32 may also include a member 86 extending across therecess 82 dividing the recess 82 into a first recess portion 82 a on afirst side of the member 86 and a second recess portion 82 b on a secondside of the member 86. In some instances, the member 86 may extendgenerally perpendicular to the recess 82 and/or the longitudinal axis ofthe housing 12. As shown in FIGS. 15A-15C, in some instances the member86 may be formed as a monolithic portion of the head portion 32 bridgingacross the recess 82. In other embodiments, however, the member 86 maybe a separate component attached to the head portion 32.

A tether 80 may extend through a passage or aperture 87 beneath themember 86 defined by the recess 82 during delivery of the implantabledevice 10, with the passage or aperture 87 connecting the first recessportion 82 a and the second recess portion 82 b. For example, the tether80 may be attached to the member 86 and extend proximally from themember 86 along an elongate shaft of a delivery device to a locationaccessible by a physician during implantation of the implantable device10. Once the implantable device 10 has been properly implanted in theheart H, the tether 80 may be detached from the member 86 and withdrawnfrom the patient.

FIGS. 16A-16C illustrate another implantable device 10 including ahelical fixation anchor 90 at the distal end 16 of the housing 12configured to be screwed into a tissue wall through rotational motion ofthe implantable device 10 to anchor the implantable device 10 to theheart H. Similar to the embodiment of FIGS. 15A-15C, the docking member30 may include an engagement feature configured to mate with anengagement feature of a delivery device to transfer rotational motionfrom a rotatable shaft of the delivery device to the implantable device10.

For example, in the embodiment of FIGS. 16A-16C, the implantable device10 may include a docking member 30 extending from the proximal end 14 ofthe housing 12 along a longitudinal axis of the housing 12. The dockingmember 30 may include a head portion 32 and a neck portion 34 extendingbetween the housing 12 and the head portion 32. The head portion 32 maybe an enlarged portion relative to the neck portion 34. For example, thehead portion 32 may have a radial dimension from the longitudinal axisof the implantable device 10 which is greater than a radial dimension ofthe neck portion from the longitudinal axis of the implantable device10.

The head portion 32 may include a recess 82 extending into the headportion 32 from a proximal surface 84 of the head portion 32. The recess82 may be configured to receive a rotational driving instrument therein.For example, the recess 82 may be configured to receive a distal drivermechanism of a rotational driving instrument therein. In some instances,the recess 82 may extend generally perpendicular to the longitudinalaxis of the housing 12. In some embodiments, the recess 82 may extendacross the head portion 32 from a first side of the head portion 32 to asecond side of the head portion 32. As shown in FIG. 16C, the headportion 32 may include a distal surface 85 opposite the proximal surface84 from which the neck portion 34 extends from. In some instances, therecess 82 may extend into the head portion 32 from the proximal surface84 toward the distal surface 85, but does not extend to the distalsurface 85. However, in other embodiments the recess 82 may extend tothe distal surface 85.

The head portion 32 may also include a member extending across therecess 82 dividing the recess 82 into a first recess portion 82 a on afirst side of the member and a second recess portion 82 b on a secondside of the member. As shown in FIGS. 16A-16C, the member may be a pin88 extending across the recess 82 or bridging across the recess 82. Insome instances, the pin 88 may extend generally perpendicular to therecess 82 and/or the longitudinal axis of the housing 12. The pin 88 maybe inserted through a hole 89 in the head portion 32 to position the pin88 across the recess 82, for example.

A tether 80 may extend through a passage or aperture 87 beneath the pin88 defined by the recess 82 during delivery of the implantable device10, with the passage or aperture 87 connecting the first recess portion82 a and the second recess portion 82 b. For example, the tether 80 maybe attached to the pin 88 and extend proximally from the pin 88 along anelongate shaft of a delivery device to a location accessible by aphysician during implantation of the implantable device 10. Once theimplantable device 10 has been properly implanted in the heart H, thetether 80 may be detached from the pin 88 and withdrawn from thepatient.

It is noted that in other embodiments the tether 80 may be attached tothe docking member 30 (such as through a passage in the docking member30) and extend proximally from the docking member 30 along an elongateshaft of a delivery device to a location accessible by a physicianduring implantation of the implantable device 10. Similarly, once theimplantable device 10 has been properly implanted in the heart H, thetether 80 may be detached from the docking member 30 and withdrawn fromthe patient.

An exemplary delivery device 100 including a rotational drivinginstrument 102 and a delivery sheath 104 is illustrated in FIG. 17A. Therotational driving instrument 102 may include an elongate drive shaft106 and a driver mechanism 108 at the distal end of the elongate driveshaft 106. The driver mechanism 108 may be configured for engagementwith the head portion 32 of the docking member 30 to transfer rotationaland/or longitudinal movement therebetween. The rotational drivinginstrument 102 may extend through a lumen 110 of the delivery sheath104. The driving instrument 102 may be rotatable and longitudinallymovable relative to the delivery sheath 104. The delivery sheath 104 maybe sized such that the implantable device 10 may be positioned in adistal region of the lumen 110, with the driving instrument 102 engagedwith a proximal portion of the implantable device 10 and extendingproximally therefrom.

The driver mechanism 108 may include a pusher 112, such as a plate,located at the distal end of the elongate shaft 106 having a distal endsurface 116 configured to engage the proximal surface 84 of the dockingmember 30. The driver mechanism 108 may also include one or more, or aplurality of protuberances, such as lugs 114, extending distally fromthe distal end surface 116 of the pusher 112, or otherwise arranged. Forexample, the driver mechanism 108 shown in FIG. 17A includes a first lug114 and a second lug 114 spaced from the first lug 114 and extending ina distal direction from the distal end surface 116 of the pusher 112.The lug(s) 114 may be configured to engage in the recess 82 of the headportion 32 of the docking member 30.

The rotational driving instrument 102 may also include a lumen 118extending therethrough. For example, the lumen 118 may extend throughthe elongate shaft 106 to an opening in the distal end surface 116 ofthe pusher 112 of the driver mechanism 108. The lumen 118 may beconfigured to receive the tether 80 therethrough such that the tether 80may extend along the delivery device 100 to a proximal region of thedelivery device 100 through the driving instrument 102. In otherinstances, the tether 80 may extend along the delivery device 100through the lumen 110 of the delivery sheath 104 and external of thedriving instrument 102, for example.

FIG. 17B illustrates an exemplary interaction between the deliverydevice 100 and the implantable device 10 with the docking member 30shown in FIGS. 15A-15C during delivery and implantation of theimplantable device 10 in a heart H, or other desired anatomy. As shownin FIG. 17B, the implantable device 10 may be positioned in the lumen110 of the delivery sheath 104 with the driving instrument 102 engagedwith the docking member 30. For instance, the distal end surface 116 ofthe pusher 112 may abut the proximal surface 84 of the head portion 32of the docking member 30 while the first lug 114 is positioned in thefirst recess portion 82 a on a first side of the member 86 and thesecond lug 114 is positioned in the second recess portion 82 b on asecond side of the member 86.

Accordingly, with the driver mechanism 108 engaged to the docking member30, rotational movement of the driving instrument 102 may be transferredto the implantable device 10 to screw the helical fixation anchor 90into a tissue wall and/or unscrew the helical fixation anchor 90 from atissue wall.

FIG. 17C illustrates an exemplary interaction between the deliverydevice 100 and the implantable device 10 with the docking member 30shown in FIGS. 16A-16C during delivery and implantation of theimplantable device 10 in a heart H, or other desired anatomy. In manyrespects the interaction may be similar to that described aboveregarding FIG. 17B. However, in FIG. 17C, the member extending acrossthe recess 82 is shown as a pin 88. Accordingly, when the drivermechanism 108 is engaged to the docking member 30, the distal endsurface 116 of the pusher 112 may abut the proximal surface 84 of thehead portion 32 of the docking member 30 while the first lug 114 ispositioned in the first recess portion 82 a on a first side of the pin88 and the second lug 114 is positioned in the second recess portion 82b on a second side of the pin 88.

Accordingly, with the driver mechanism 108 engaged to the docking member30, rotational movement of the driving instrument 102 may be transferredto the implantable device 10 to screw the helical fixation anchor 90into a tissue wall and/or unscrew the helical fixation anchor 90 from atissue wall.

FIGS. 18A-18D illustrate alternative embodiments of a driver mechanism108 for a rotational driving instrument 102 configured to mate with adocking member of an implantable device, such as one or more of thedocking members 30 of the implantable device 10, described herein.

The driver mechanism 108 shown in FIGS. 18A-18C may be similar to thedriver mechanism 108 shown in FIGS. 17A-17C. For example, the rotationaldriving instrument 102 may include an elongate drive shaft 106 and adriver mechanism 108 at the distal end of the elongate drive shaft 106.The driver mechanism 108 may be configured for engagement with the headportion 32 of the docking member 30 to transfer rotational and/orlongitudinal movement therebetween. The rotational driving instrument102 may extend through a lumen 110 of the delivery sheath 104 (shown inFIG. 17A).

The driver mechanism 108 may include a pusher 112 having a distal endsurface 116 configured to engage the proximal surface 84 of the dockingmember 30 and one or more, or a plurality of protuberances, such as lugs114, extending distally from the distal end surface 116 of the pusher112. For example, the driver mechanism 108 shown in FIG. 18A includesfour equally spaced apart lugs 114, the driver mechanism 108 shown inFIG. 18B includes three equally spaced apart lugs 114, and the drivermechanism 108 shown in FIG. 18C includes four equally spaced apart lugs114 extending in a distal direction from the distal end surface 116 ofthe pusher 112. The lug(s) 114 may be configured to extend into openingsbetween adjacent spokes 70 of the docking members 30 described herein,and engage in the spokes 70 of the head portion 32 of the docking member30 to transfer rotational torque therebetween.

The rotational driving instrument 102 may also include a lumen 118extending through the elongate shaft 106 configured to receive thetether 80 therethrough such that the tether 80 may extend along thedelivery device 100 to a proximal region of the delivery device 100through the driving instrument 102. In other instances, the tether 80may extend along the delivery device 100 through the lumen 110 of thedelivery sheath 104 and external of the driving instrument 102, forexample.

The shape, size, quantity and arrangement of the lugs 114 may be chosento complement and mate with the shape, size, quantity and arrangement ofspokes 70 of the docking member 30. For example, the lugs 114 shown inFIG. 18C, may be triangular or wedge shaped to fit between adjacentspokes 70 of the docking member 30 shown in FIG. 8A, 9A, 10A or 14A. Inother instances, the shape of the lugs 114 may be chosen to complementand mate with the spokes 70 shown in FIG. 11A, 12A or 13A, for example.

In other instances, as shown in FIG. 18D, the driver mechanism 108 ofthe rotational driving instrument 102 may include a socket 120 shaped,sized and configured to mate with the head portion 32 of the dockingmember 30 to transfer rotational torque therebetween. For example, asshown in FIG. 18D, the socket 120 may include opposing arcuate edges andopposing flat edges extending between the arcuate edges, configured tocomplement the shape and size of the docking member 30 shown in FIG. 4A.The flat edges of the socket 120 may engage the flat sides of thedocking member 30 to transfer rotational torque therebetween. It isnoted that in some instances, the socket 120 may include a single flatside for engagement with a flat side of the docking member 30.

In other instances, the socket 120 may have another shape, size andconfiguration to mate with the head portion 32 of another docking member30. For example, the socket 120 may include a complementary shape, sizeand configuration to the head portion 32 of the docking member 30 shownin FIG. 8A, 9A, 10A, 11A, 12A, 13A or 14A such that the head portion 32of the docking member 30 fits into the socket 120. The socket 120 mayinclude at least one edge or surface configured to engage a surface ofthe head portion 32 of the docking member 30 to transfer rotationaltorque therebetween.

Those skilled in the art will recognize that aspects of the presentdisclosure may be manifested in a variety of forms other than thespecific embodiments described and contemplated herein. Accordingly,departure in form and detail may be made without departing from thescope and spirit of the present disclosure as described in the appendedclaims.

What is claimed is:
 1. An implantable leadless cardiac pacing devicecomprising: a housing having a proximal end and a distal end; anelectrode positioned proximate the distal end of the housing configuredto be positioned adjacent cardiac tissue; and a docking member extendingfrom the proximal end of the housing along a central longitudinal axisof the housing, the docking member configured to facilitate retrieval ofthe implantable leadless cardiac pacing device; the docking memberincluding a head portion centered on the central longitudinal axis and aneck portion centered on the central longitudinal axis, the neck portionextending between the housing and the head portion; the head portionhaving a radial dimension measured from the central longitudinal axis toan outer peripheral surface of the head portion and the neck portionhaving a radial dimension measured from the central longitudinal axis toan outer peripheral surface of the neck portion, wherein the radialdimension of the neck portion is less than the radial dimension of thehead portion; the head portion including a recess extending into thehead portion from a proximal surface of the head portion to aproximally-facing surface formed within the head portion; wherein therecess opens out to the peripheral surface of the head portion and theproximal surface of the head portion.
 2. The implantable leadlesscardiac pacing device of claim 1, further comprising a member extendingacross the recess.
 3. The implantable leadless cardiac pacing device ofclaim 2, wherein the member extends generally perpendicular to therecess.
 4. The implantable leadless cardiac pacing device of claim 3,wherein each of the member and the recess extend generally perpendicularto the central longitudinal axis of the housing.
 5. The implantableleadless cardiac pacing device of claim 2, wherein the member dividesthe recess into a first portion on a first side of the member and asecond portion on a second side of the member.
 6. The implantableleadless cardiac pacing device of claim 5, wherein the first portion ofthe recess opens out to the outer peripheral surface of the head portionon a first side of the head portion and the second portion of the recessopens out to the outer peripheral surface of the head portion on asecond side of the head portion opposite the first side of the headportion.
 7. The implantable leadless cardiac pacing device of claim 2,further comprising a tether attached to the member.
 8. The implantableleadless cardiac pacing device of claim 1, wherein the recess extendsacross the head portion from a first side of the head portion to asecond side of the head portion.
 9. The implantable leadless cardiacpacing device of claim 1, wherein the head portion is a knob having afirst diameter and the neck portion has a second diameter less than thefirst diameter.
 10. The implantable leadless cardiac pacing device ofclaim 1, wherein the head portion has a distal surface opposite theproximal surface from which the neck portion extends from, wherein therecess does not extend to the distal surface.
 11. An implantableleadless cardiac pacing device comprising: a housing having a proximalend and a distal end; an electrode positioned proximate the distal endof the housing configured to be positioned adjacent cardiac tissue; anda docking member extending from the proximal end of the housing along alongitudinal axis of the housing, the docking member configured tofacilitate retrieval of the implantable leadless cardiac pacing device;the docking member including a head portion and a reduced diameter neckportion extending between the housing and the head portion; the headportion having a proximal surface and an outer circumferential surface;the head portion including a recess extending laterally across the headportion from a first location on the outer circumferential surface on afirst side of the head portion to a second location on the outercircumferential surface on a second side of the head portion oppositethe first side of the head portion relative to the longitudinal axis;wherein the recess is at least partially defined by a proximally-facingsurface formed within the head portion.
 12. The implantable leadlesscardiac pacing device of claim 11, further comprising a member extendingacross the recess.
 13. The implantable leadless cardiac pacing device ofclaim 12, wherein the member divides the recess into a first portion ona first side of the member and a second portion on a second side of themember.
 14. The implantable leadless cardiac pacing device of claim 13,wherein the head portion includes an aperture below the member, theaperture connecting the first and second portions of the recess.
 15. Theimplantable leadless cardiac pacing device of claim 14, furthercomprising a tether attached to the member.
 16. The implantable leadlesscardiac pacing device of claim 15, wherein the tether passes through theaperture.
 17. The implantable leadless cardiac pacing device of claim12, wherein the member is formed as a unitary portion of the dockingmember.
 18. The implantable leadless cardiac pacing device of claim 11,wherein the member is a pin disposed in a bore of the docking member.19. The implantable leadless cardiac pacing device of claim 11, whereinthe recess extends into the head portion from the proximal surface. 20.The implantable leadless cardiac pacing device of claim 19, wherein thehead portion has a distal surface opposite the proximal surface fromwhich the neck portion extends from, wherein the recess does not extendto the distal surface.